Doug Beretta, who runs an organic dairy farm in Santa Rosa, always welcomes the spring arrival of daylight-saving time. His cows, on the other hand, have a bigger problem with the switchover, which this year starts on Sunday.

"From our standpoint, it gives us an extra hour of daylight at night, so we're able to get more things done," says Beretta. "(But) for the first week or so, it's tough for the cows to adjust."

Sunday at 2 a.m., when clocks should be set forward one hour, marks the earliest time change since 1974. It's the second year in a row that daylight saving begins on the second Sunday in March instead of the first Sunday in April.

The extra hour of daylight will last until Nov. 2, which for Beretta will mean a more efficient farm. But for every spring change, Beretta adjusts the milking times for his cows by 30 minutes. Normally, his 300 cows are milked first at 2 a.m. With the time change, this normal time essentially becomes 3 a.m., so Beretta moves the morning milk time to 2:30 a.m. In the fall, when clocks are turned back an hour, the cows' adjustment is more difficult.

"When you move it back, those cows are holding that milk for an extra hour, so you can run into some health problems," he said.

Ideally, said Beretta, the government would stick to one time standard all year round. "I just wish it would stay set," he said. "It's cumbersome to get all your clocks changed. I wonder if it's worth all the hassle."

The biannual spring/fall time adjustment has been in effect for most of the past 90 years, ever since World War I prompted Congress to find a dramatic way to save Americans money and stimulate the economy. Washington's logic: With more daylight hours, households would spend less on bills for lighting and electricity; also, factories would be more efficient because workers would be refreshed with the extra daylight hours they had for unwinding.

After President Bush signed the Energy Policy Act of 2005, which extended daylight-saving time by a month, the Department of Energy touted the benefits of energy savings, but Michael Downing, who detailed the history of daylight-saving time in a 2005 book, says the U.S. government has misled Americans on the economic benefits of the time switch. The biggest beneficiaries of the spring clock change aren't consumers but retailers. People shop more when there's more light at night.

"There's a reason that the first and most persistent lobby for daylight-saving was the Chamber of Commerce on behalf of retailers and merchants," says Downing, a lecturer at Tufts University outside Boston. "People really bought more goods after work when they were given light. And that effect persists. As recently as 1986, when we went from six months of daylight saving to seven, that extra month, according to industry estimates, was worth $200 million-$400 million to the golf industry alone, and $150 million to the barbecue industry."

Oil companies also lobbied for daylight-saving time because they predicted - correctly - that it would lead to more leisure driving, Downing said.

The Parent-Teachers Association is among the groups that have opposed daylight-saving time because, in the spring, it means students go to school when it's still dark. The PTA's concerns took on national prominence in 1974, after President Nixon mandated that daylight-saving time take effect in January. Nixon wanted to reduce Americans' electricity bills in the wake of OPEC's oil embargo, which drove up gas prices.

"Within a week, pictures started to flash around the nation of kids on these dark streets," Downing says. "There were a couple of bus accidents involving schoolchildren, and that became the end of Nixon's plan."

Sunday's time switch is the earliest for Americans since Nixon's experiment. Last year's change in time caused some confusion for computer users. This year, experts expect no trouble and say that most computer operating systems should automatically roll over to the correct time.

Though the title of Downing's book, "Spring Forward: The Annual Madness of Daylight Saving Time," would indicate he opposes the time switch, Downing doesn't. Like Beretta, Downing enjoys the extra moments he gets with the sun still overhead.

"Most people like having extra light in the summer at the end of the day - it absolutely effects a behavioral change," says Downing, who lived in the Bay Area on and off for three years. "If you give people more light at the end of the day, they'll go outside their houses. ... I'm a devoted fan of long, late summer sunsets. So I'm all for daylight saving during the longest days of the year."